DESCRIPTION (Applicant's Abstract): There is currently limited consensus on the most effective intervention designs for HIV prevention in developing countries. Decisions on which type of projects to fund, who should be targeted with interventions, and how to design prevention programs have not been based on comparisons of the cost-effectiveness of interventions. A major problem in forging consensus on these issues is that available data do not link costs to effectiveness measures. Standardization of costs and outcomes across populations, regions, and interventions has also been unavailable. This project will calculate and compare standardized measures of the cost-effectiveness of interventions for prevention of HIV and Sexually Transmitted Infections (STI) across types of interventions, geographic regions,and target populations using data from actual HIV/STI intervention projects in Africa, Latin America, and Asia. The sex projects selected for evaluation are all associated with the AIDSCAP project, funded by the US Agency of International Development, and include: (1) a comprehensive sex worker intervention in the Dominican Republic, (2) a peer-education and counseling intervention for men who have sex with men in the Dominican Republic, (3) a STD and peer-education intervention for sex workers in Tanzania, (4) a community-based prevention program in rural Tanzania, (5) a factory worker intervention in Thailand, and (6) a comprehensive HIV and STD intervention targeting poor women in Bangkok, Thailand. Comprehensive and standardized behavioral evaluation data are available for all sites, and cost data will be collected in the initial phase of the project. Retrospective control data on similarly unexposed populations will also be compiled and analyzed for each intervention site. The primary outcome of interest in the discounted cost per HIV case averted, and the cost per Quality Adjusted Life Year (QALY) for each intervention. This project will also help develop the applicant's skills and experience in conducting modeling and health economic analysis.